Vehicle systems in which a carrier for articles and objects of diverse types is movable along a track are disclosed for example, in U.S. Pat. No. 3,948,187 and generally comprise a track which can be endless and establishes a path along which the carrier can be propelled or can move in free or gravitationally-induced movement.
The carrier may be one of a number of carriers which can have selector means enabling a variety of destinations along the path to be selected, and various stations can be provided along the path for introducing carriers, as individual vehicles, onto the path or withdrawing the vehicles from the path.
The aforedescribed systems have found application wherever an organized distribution or delivery of raw, semifinished or finished materials is required in manufacturing plants to assist in the collection and distribution of objects in commercial and governmental installations, and to enable access to inventoried stock in warehousing and like applications.
The vehicles themselves may be self-propelled, may be entrained over a portion of the path by conveyors or drive members of diverse type, and may move over at least a portion of the path by inertia or gravitational action.
It has been found to be desirable to provide a stop device along the path of such carriers or vehicles which responds to an excessive vehicle speed, e.g. a speed of the vehicle above a predetermined speed which may be the maximum safe speed of the vehicle.
In the aforementioned patent, for example, an arm extends into the path of the vehicles and is engaged thereby to activate a pin which is released when the vehicle exceeds the predetermined limiting speed so that a latch disengages a gravitationally biased member which swings into the path of the carrier to stop the latter.
While this system has been found to be highly effective, there are some difficulties which are inherent in its construction which have impeded its use. For example, the reliance upon gravitational forces precludes positioning the stop device except in horizontal-track applications. Furthermore, the frictional release mechanism must overcome significant frictional forces to be effective and these forces tend to increase as the release or latch mechanism becomes contaminated with dirt. As a result, the threshold velocity of the vehicle at which the device responds, tends to increase with time.